The USPSTF found inadequate evidence to determine the extent to which the added detection offered by ECG, ETT, or EBCT (beyond that obtained by ascertainment of conventional CHD risk factors) (see Clinical Considerations) would result in interventions that lead to improved CHD-related health outcomes among adults at increased risk for CHD events. Although there is limited evidence to determine the magnitude of harms from screening this population, harms from false-positive tests (that is, unnecessary invasive procedures, overtreatment, and labeling) are likely to occur. As a result, the USPSTF could not determine the balance between benefits and harms of screening this population for CHD.

Clinical Considerations

Several factors are associated with a higher risk for CHD events (the major ones are nonfatal myocardial infarction and coronary death), including older age, male gender, high blood pressure, smoking, abnormal lipid levels, diabetes, obesity, and sedentary lifestyle. A person's risk for CHD events can be estimated on the basis of the presence of these factors. Calculators are available to ascertain a person's risk for a CHD event; for example, a calculator to estimate a person's risk for a CHD event in the next 10 years can be accessed at http://hin.nhlbi.nih.gov/atpiii/calculator.asp?usertype=prof. Although the exact risk factors that constitute each of these categories (low or increased risk) have not been established, younger adults (that is, men <50 years of age and women <60 years of age) who have no other risk factors for CHD (<5% to 10% 10-year risk) are considered to be at low risk. Older adults, or younger adults with one or more risk factors (>15% to 20% 10-year risk), are considered to be at increased risk.

Screening with ECG, ETT, and EBCT could potentially reduce CHD events in 2 ways: either by detecting people at high risk for CHD events who could benefit from more aggressive risk factor modification or by detecting people with existing severe CAS whose life could be prolonged by coronary artery bypass grafting (CABG) surgery. However, the evidence is inadequate to determine the extent to which people detected through screening in either situation would benefit from either type of intervention.

The consequences of false-positive tests may potentially outweigh the benefits of screening. False-positive tests are common among asymptomatic adults, especially women, and may lead to unnecessary diagnostic testing, overtreatment, and labeling.

Because the sensitivity of these tests is limited, screening could also result in false-negative results. A negative test does not rule out the presence of severe CAS or a future CHD event.

For people in certain occupations, such as pilots and heavy equipment operators (for whom sudden incapacitation or sudden death may endanger the safety of others), considerations other than the health benefit to the individual patient may influence the decision to screen for CHD.

Although some exercise programs initially screen asymptomatic participants with ETT, there is not enough evidence to determine the balance of benefits and harms of this practice.

Discussion

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Coronary heart disease is the leading cause of death in the United States; more than 700 000 of the deaths in 2000 were due to heart disease (1). The overall costs of CHD and stroke in 2003 are estimated to be greater than $350 billion (2).

Many clinicians ascertain a person's overall risk for CHD events by screening for cardiac risk factors and incorporating that information into risk prediction equations derived from the Framingham or other cohort studies (3, 4). Asymptomatic adults clearly benefit from risk factor modification proportional to their degree of CHD risk (that is, more intensive risk factor modification for people at higher risk) (5). Since those at high risk for CHD may already be receiving interventions to maximally reduce their risk for CHD events, screening may potentially be of greatest benefit to those presumed to be at intermediate risk for CHD who could be reclassified as being at high risk (and thus treated more aggressively) after additional testing. In addition to risk factor reduction, persons with symptoms of CHD who have severe CAS (defined as either triple-vessel or left main coronary artery atherosclerotic disease with poor left ventricular function) clearly benefit from CABG or percutaneous transluminal coronary angioplasty (6-8). Among the asymptomatic population, those at higher risk for CHD events have a higher prevalence of severe CAS; thus, the yield of screening is expected to be greater in this population. However, it is uncertain whether this increased yield increases the detection of people with severe CAS to an important degree and whether invasive revascularization procedures would benefit those who are asymptomatic as much as those who have symptoms of CAS.

The USPSTF reviewed the evidence as to whether supplementing the conventional CHD risk ascertainment strategy with additional screening using ECG, ETT, or EBCT, or using these 3 tests to identify people with severe CAS earlier, would lead to improved health outcomes in asymptomatic persons. The USPSTF found no randomized, controlled trials with health outcomes that examined the extent to which ECG, ETT, or EBCT scanning for coronary calcium provided additional prognostic information beyond the currently used risk factor calculations. The Task Force further found that the 3 screening tests—ECG, ETT, and EBCT—have poor to fair accuracy in predicting CHD events.

Systematic reviews have reported that the sensitivity of resting ECG abnormalities for CHD events is low (3, 9). The prevalence of the most common ECG abnormalities (Q waves, left ventricular hypertrophy, bundle-branch blocks, and ST-segment depression) ranges from 1% to 10% (3). Only a few studies have examined ECG abnormalities in the black population. Although major ECG abnormalities may be more prevalent in black men than in white men, these abnormalities may not confer the same risk for CHD death in black men (relative risk, 1.95 [95% CI, 0.93 to 4.11]) as in white men (relative risk, 2.72 [CI, 1.47 to 5.04]) (10).

The sensitivity of ETT for the prediction of CHD events 3 to 12 years in the future ranges from 40% to 62%; the positive predictive value (PPV) ranges from 6% to 48%. The higher sensitivity of ETT reported in older studies may not be accurate because of the possibility of spectrum bias (11, 12). The prevalence of an abnormal ETT (ST-segment depression 1 mm) reportedly ranges from 5% to 25% (3). The yield of ETT in detecting severe CAS in asymptomatic middle-aged men is estimated to be 0.5% (3, 13). The PPV for future CHD in recent cohort studies (most of them conducted with asymptomatic men) is low (range, 6% to 48%) (3). Adding nuclear perfusion to ECG analysis may increase sensitivity somewhat; however, the low PPV of ETT is due mainly to the low prevalence of CHD in asymptomatic persons and cannot be corrected simply by improving test accuracy.

For patients with symptoms of CHD, EBCT has a sensitivity of 80% and a specificity of 40% for detecting angiographically demonstrated CAS (14); similar data for those who have no symptoms are lacking. A systematic review reported that higher calcium scores on EBCT were associated with higher risk for CHD events (3). This review concluded that EBCT may have a role in better defining risk for CHD events in those who have been identified as being at intermediate risk based on traditional risk factors, but no study has examined the effect of EBCT data on clinical decision making (3).

Potential harms of screening asymptomatic patients for CHD include unnecessary invasive testing (for example, coronary angiography) and "labeling" of those who have had false-positive test results. In low-risk asymptomatic populations, most positive ECG test results occur in those who will not have a CHD event in the next 5 to 10 years (3). One study reported that 71% of those without symptoms who had an abnormal ETT had no angiographically demonstrable CAS (15). While the yield of screening is low in those at low risk for CHD, the potential for harm from false-positive tests is high. The USPSTF judged that the benefits of screening people at low risk for CHD would not outweigh the potential harms.

Because of the limited sensitivity of resting ECG and the low prevalence of CHD in asymptomatic adults, a majority of CHD events will occur among those with an initially normal ECG (that is, those who test false negative) (16). The ETT can be normal or nondiagnostic in a large proportion of patients who will go on to have a CHD event, which may be explained partly by the fact that many acute CHD events result from sudden occlusion of a previously unobstructed artery segment (17).

A large study, the Multi-Ethnic Study of Atherosclerosis (MESA), is ongoing. Data from this study will help to examine the independent prognostic information derived from EBCT in the context of accurate measurement of traditional risk factors and extended follow-up (18). In the absence of such data for ECG, ETT, or EBCT, the USPSTF concluded there is insufficient evidence to recommend for or against screening for CHD.

Recommendations of Others

The American College of Cardiology/American Heart Association (ACC/AHA) gave a class III recommendation for screening with exercise testing in asymptomatic persons without known coronary artery disease (CAD). For the evaluation of those with multiple risk factors as a guide to risk-reduction therapy, and for the evaluation of asymptomatic men older than 45 years of age and women older than 55 years of age who a) plan to start vigorous exercise, b) are involved in occupations in which impairment might impact public safety, or c) are at high risk for CAD because of other diseases, the ACC/AHA gave screening with exercise testing a class IIb recommendation. For the evaluation of asymptomatic persons with diabetes who plan to start vigorous exercise, the ACC/AHA gave screening with exercise testing a class IIa recommendation (19). The ACC/AHA Writing Group does not recommend EBCT to diagnose obstructive CAD (14). The American Academy of Family Physicians does not recommend use of routine ECG as part of a periodic health or a preparticipation physical examination in either asymptomatic children or adults (20).

Appendix

Members of the U.S. Preventive Services Task Force are Alfred O. Berg, MD, MPH, Chair (University of Washington, Seattle, Washington); Janet D. Allan, PhD, RN, CS, Vice-Chair (University of Maryland Baltimore, Baltimore, Maryland); Ned Calonge, MD, MPH (Colorado Department of Public Health and Environment, Denver, Colorado); Paul Frame, MD (Tri-County Family Medicine, Cohocton, and University of Rochester, Rochester, New York); Joxel Garcia, MD, MBA (Pan American Health Organization, Washington, DC); Russell P. Harris, MD, MPH (University of North Carolina School of Medicine, Chapel Hill, North Carolina); Mark S. Johnson, MD, MPH (University of Medicine and Dentistry of New Jersey–New Jersey Medical School, Newark, New Jersey); Jonathan D. Klein, MD, MPH (University of Rochester School of Medicine, Rochester, New York); Carol Loveland-Cherry, PhD, RN (University of Michigan, Ann Arbor, Michigan); Virginia A. Moyer, MD, MPH (University of Texas at Houston, Houston, Texas); C. Tracy Orleans, PhD (The Robert Wood Johnson Foundation, Princeton, New Jersey); Albert L. Siu, MD, MSPH (Mount Sinai School of Medicine, New York, New York); Steven M. Teutsch, MD, MPH (Merck & Co., Inc., West Point, Pennsylvania); Carolyn Westhoff, MD, MSc (Columbia University, New York, New York); and Steven H. Woolf, MD, MPH (Virginia Commonwealth University, Fairfax, Virginia). This list includes members of the Task Force at the time this recommendation was finalized. For a list of current Task Force members, go to http://www.ahrq.gov/clinic/uspstfab.htm.